The invention relates to a camera comprising:
a lens system for focusing the image of a subject on a sensitive plate,
an image processing device utilizing filters for performing an image compression transformation,
a control system acting on the lens system to ensure a sharp image of the subject on the sensitive plate, the system comprising at least a first high-pass image filter and a first low-pas image filter in the form of summers of the results of the compression transformation.
The invention also relates to a focusing method for a camera.
The invention finds its application in digital cameras.
To obtain a proper focusing and thus a sharp image it is known that the transactions in the image are analyzed because they are often more abrupt on the subject to be photographed than on the background. It is estimated that the focal distance of the lens of the camera is optimal when the transitions in the image are the most abrupt.
The present invention proposes a camera for which the focusing is effected in a simple manner without needing too much additional material.
Therefore, such a camera is characterized in that said image filters utilize the filters of the image-processing device.
A focusing method utilized in a camera that comprises an image processing circuit in the form of high-pass and low-pass image filters is characterized in that it comprises the following steps:
estimation of the value of the output of at least one of said high-pass filters,
normalization of this value by means of the value of the output of a low-pass filter,
control of the focusing system with a view to obtaining a maximum value of the normalized signal,
release for taking the photo if the normalized value exceeds a certain threshold.